Expansible piston



May 14, 1929. G; c, r-fAKlhJsl 1,713,031 u ExPANsIBLE PIsToN Filed Dec.51, 1924 titl llilntented lid, lt

Mmm

.application filed llecembcr 341,

This invention has to do with pistons ot .the pistono is among theobjects oit the invention to provide a piston of this type which is otcomparatively cheap and simple construction; a piston which is easilyassembled or talren dovvn :tor replacement and repair; and one which is:tally eltective in operation.

ll provide a packing ring ot elastic inaterial llyetvveen tvvo rigidmembers on the piston rod, and by Jforcing these two members together,considerable end pressure is exerted on the ring trom opposite sidesthereoi'. Vltliere are passageways in the piston head leading trom thecylinder bore to the paclring ring, these passageways serving to directtluid under pressure Within the cylinder against the inner peripheraltace oit the ring, The tluid pressure is thus adapted to expand the ringinto tight engagement with the cylinder Walls. its the ring vvearsdovvn, the tluid pressure continuously expands the ring so its tightengaeement vvitli the cylinder is maintained..

ne et the Jteatures ot my invention lies in the provision ot means torretaining the paclring in expanded position when the fluid pressuredrops. lorinstance, suppose the pressure is suliiciently great to havecnpanded the packing into proper engagement v`with the cylinder, andthen drops such an amount that the resiliency oi the packing tends tocontract the packing sufliciently to draw it avvay it'rom tho cylinderwalls. There -would then be an undesirably loose lit between piston andcylinder until the tluid pressure is again raised. By reason oit theprovisions l make, the ring is held to 'the position it takes undermaximum fluid pressure and the above mentioned objectionable conditionsare avoided,

ow this is done will be fully set forth in the Jfollowing detailedspeciiication, wherein other objects and novel features ot the inventionvvill be made apparent. ltteterence vvill be made to the accompanyingdrawings, in which:

It is a longitudinal, medial section through a pump piston embodying myiiivention; and

lHig. 2 is a transverse section on line oit 1.

lin the drawings, numeral 1U designates a pump cylinder through vvhich apiston made up ot head 11 on rod 12 is adapted to reciprocate. ll Willdescribe piston 11 as being made up in a particular manner and mountedon rod 12 in a certain way, but it Will be understood theseparticularities oit construction are not necessary to the invention,considered in its broader aspects, and

are not to be considered limitative on the broader claims appendedhereto.

lttod 12 has a tapered portion 13 and an eirtrenriity 1li ot reduceddiameter, the latter being threaded at 15 along a portion ot its extentl ltllead 11 includes tvvo rigid and substan tially cylindrical members16 and 1l' mounted on rod 12 in the manner clearly illustrated in Fig.1, betvveen which is clamped an elastic (rubber, 'tor instance) packingringAl 18. Members 16, 17 have peripheral flanges 19 which define thesides ot channel 2t) When the members are assembled on rod 12. Theopposed faces 21 ot flanges 1 9 may be roughened or corrugated toprovide ttor the better gripping ot the end 'tacos ot ring 12.

lltingl has internal Hangs 22 adapted to extend between the opposed endlaces 23 ot members 16 and 1"?, one oit the members (16, 'tor instance)preterably having a hub 2t projecting partially into the bore ot dange22.

ll/llovement ot member 1d to the right (as viewed in lliig. 1) along rod12 is limited by the taper 13 ot rod 12 or by engagement ot said memberwith rod shoulder 25.

lt is evident that by setting up nuts 26 titl tid

litt

lltld member 1i' is moved longitudinally along l rod 12 in a manner tocompress ring 18 between flanges 19 and to compress tlange 22 betweentacos 23. If desired, spacers or Washers 26u may be interposed betweenhub 24 and the tace 23 of member 17 to limit the movement of the tvvomembers towards each iet other and to avoid undue looseness. Washers 26awill be provided in varying thicknesscs so a proper cho-ice may be madefor a given installation.

'Ihe described longitudinal compression of ring 18 expands it indiameter and into tight engagement with the walls of cylinder 10. Inorder to facilitate this expansion and to give the ring uniformdiametral expansion throughout, I may provide diagonal surfacesl 27 onthe two members between their peripheral faces and faces 23; ring 18having a complementary or fillet formation at 28 between the under faceof the ring and the side faces of flange 22. When members 16 and 17 areforced together, faces 27 squeeze the center part of ring 18 outwardlyso said center part is expanded substantially equally with the edgeparts of the rino.

lf/Iembers 16 and 17 each have several ports 29 through which liquidpressure from cylinder 12 is directed beneath ring 18. For instance,when the piston travels to the rlght (as viewed in Fig. 1) the liquidpressure raised to the right of head 11 passes through ports 29 inmember 1G and acts against the innerperipheral face of ring 18 at theright handend thereof, tending to push that end of the ring outwardlyand. more tightly into engagement with the wall of lcylinder 12. Duringthis action, the

' right hand end or edge of the ring slips outwardly where it bears aainst the side face of flange 19, and, since t e head is compressing t ering longitudinally, there is considerable pressure between said ring ede and flange and the ring will thereby be he d in expanded position.Such action occurs when the ring wears, the wear being thusautomatically compensated since the liquid pressure expands the ring vasfast as wear occurs. Further, it will be seen that even after thepressure drops or is entirely released, the ring is held in the positionof expansion it assumed under maximum pressure, by virtue of thecontinuous exertion of clamping or end pressure set up by nuts 26.

The roughenmg or corrugating of flange faces 21 assist in gripping ring18 to prevent its contraction after a pressure drop.

Preferably, the normal thickness of flange 22 and the normal size offillets is such that flange and fillets are put under considerableexcess pressure when a packing ring of given width is clamped betweenflanges 19. Therefore, the center part of ring 18 is expandedpractically to the same extent as are its end parts when acted upon byliquid pressure. After the ring wears to a certain extent, the tendencyof liquid pressure beneath the end parts of the ring is to eX- pand thering out of engagement with the peripheral faces ofl members 16 and 17,flange 22 being drawn radially between faces 23 by such ring movement.The squeezing effect of diagonal faces 27 on fillets 28 aids in thusmoving flange 22 outwardly or radially so the center part of the ringdoes not lag behind the end parts and the, entire extent of theperipheral face of the ring is held against the cylinder walls withsubstantially uniform pressure.

It will be evident that various changes in design, striurture andarrangement may be made -without departing from the spirit and scope ofthe invention. For instance, the compression of ring 18 may be broughtabout by means other than nuts 26, or a member capable of relativemovement with respect to member 16 may be utilized for clamping the edgeof ring 18. rlfhe drawings and description are to be considered merelyas illustrative of and not restrictive on the following claims.

Having described a preferred form of my invention, I claim:

1. A plston head adapted to be reciprocated through a cylinder,embodying rigid members having opposed, spaced shoulders, a ring ofelastic parking around the head and between the shoulders, an infernalflange on the ring, one of said members being movable longitudinally ofthe head axis towards and away from the other member, means for movingsaid member to compress the ring between said shoulders and to clamp thefiange between the members; there being a passageway in the head leadingfrom the cylinderbore to the underside of the ring whereby fluid underpressure within the cylinder is directed beneath the ring to expand itradially into engagement with the cylinder walls, and the endpressureexerted on the ring by virtue of its compression between saidshoulders being adapted to hold the ring in expanded position.

2. A piston adapted to be reciprocated through a cylinder and embodyinga piston rod, two substantially cylindrical body menibers on the rod,each of the members having a peripheral flange which, with theperipheral faces of the members, define a channel about the head whenthe members are assembled on the piston rod, an elastic pachingringwithin the channel, an internal fiange on the ring and extending betweenthe opposed faces of the members below the channel, and means forforcing the members together on the rod to clamp the ring fiange betweensaid faces and to compress the ring within the channel; there beingpassageways leading from the cylinder bore to the peripheral definingwall of the channel whereby fluid under pressure within the cylinder isadmitted to the channel beneath the ring to expand it radially intoengage.- inent with the cylinder walls, and the end pressure exerted onthe rin ,I by the channel defining walls of the perip feral flangesheiyiaoai ing adapted to hold the ring in expanded position.-

3. l piston structure embodying a head including two cylindrical membersmounted on a piston rod, each member having a peripheral ida-nge which,with the peripheral laces ol the members, deline an annular periphcralchannel about the head, an elastic paclring ring in the channel, aninternal llange on the ring extending inwardly of the ring between theend laces of the members inward ol the channel, tillets integral withthe ring at the point ot' internal ange junction therewith, the opposedfaces of said members inward of the channel being formed substantiallycomplementary to said lillets, so that upon movement of the membertoward each other the said opposed laces act on said hllets to forcethem and the ring outwardly; and means 'for forcing the members togetheron the rod for compressing the ring and its flange longitudinallybetween them and radially expanding the ring.

4. In a piston head adapted to be reciprocated through a cylindelg'abody comprising two parts with opposing peripheral annular shouldersdefining an annular channel be tween them and hailing opposing facesinward ot the channel, an elastic packing ring tting tightly andcompressed axial y be tween the opposed annular shoulders and haying acentral inwardly extending annular flange clamped between the saidopposing surfaces; and the body parts having passages admitting lluidpressure trom each end of the piston head to the annular ohannelunderthe ring at each side et its dange.

5. ln a piston head adapted to be reciprocated through a cylinder, abody comprisl ing two parts with opposing peripheral annular shouldersdefining an annular channel between them and having opposing lacesinward of the channel, an elastic packing ring in the channel and havingan integral4 elastic inwardly extending annular flange in its centralpart clamped between the said opposing surfaces; and the body partshaving passages admitting fluid pressure from each end of the pistonheadto the channel under the ring at each side of its flange.

In Witness that I claim the foregoing I have hereunto subscribed my namethis 25th day of November, 1924.

GROVER C. DEAKINS.

